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ZOJ Problem Set - 2766
Local Maxima

Time Limit: 2 Seconds      Memory Limit: 65536 KB

For a permutation, we call the element which is larger than any of its successors as "local maxima". Your task is to calculate the average number of local maxima in a random permutaion of n elements.

Input

The input contains multiple cases. In each case, there is a single integer n (1<=n<=2^31-1) indicating the number of elements of the permutation.

Output

Ouput the average number of local maxima in a single line. Accurate the result up to 8 decimal numbers.

Sample Input

1
2

Sample Output

1.00000000
1.50000000

Author: FAN, Xiang
Source: ZOJ Monthly, October 2006
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